Creating lenticular galaxies with major mergers

TL;DR

This paper demonstrates through N-body simulations that major mergers of spiral galaxies can produce lenticular galaxies, aligning with observational data and challenging previous fading-based formation theories.

Contribution

It provides the first simulation-based evidence that major mergers can form lenticular galaxies consistent with observed photometric properties.

Findings

Major mergers increase light concentration in resulting lenticulars.

Mergers reduce angular momentum compared to spiral progenitors.

Results align with CALIFA observations, challenging fading scenarios.

Abstract

Lenticular galaxies (S0s) represent the majority of early-type galaxies in the local Universe, but their formation channels are still poorly understood. While galaxy mergers are obvious pathways to suppress star formation and increase bulge sizes, the marked parallelism between spiral and lenticular galaxies (e.g. photometric bulge-disc coupling) seemed to rule out a potential merger origin. Here, we summarise our recent work in which we have shown, through N-body numerical simulations, that disc-dominated lenticulars can emerge from major mergers of spiral galaxies, in good agreement with observational photometric scaling relations. Moreover, we show that mergers simultaneously increase the light concentration and reduce the angular momentum relative to their spiral progenitors. This explains the mismatch in angular momentum and concentration between spirals and lenticulars recently revealed by CALIFA observations, which is hard to reconcile with simple fading mechanisms (e.g. ram-pressure stripping).